Krillin by statements. Tien by feats and probably logic too at this stage. All he does is train and that training allows him to do two things that make no sense even if he were hundreds to a thousand times stronger in the Semi-Perfect feat and him deflecting an attack meant to kill Gohan in Buutenks. If his training allows him to reach those levels of rubber band AI then he can probably one shot Krillin before he starts training and getting dommed by 18.
At base levels where Tien isn't straining his life, probably Krillin. Krillin doesn't really do anything in Z until training with 18 though, and he was shit in Dragon Ball far below Tien, so it's reliant entirely on statements from outside sources. His only real feats are beating Saibaman and Frieza henchmen. Gets big powerup, does nothing. Frieza's tail I guess, but doubtful Tien lets himself get hit by that.
Not necessarily. Yamcha, in the manga, said he is currently in the top 3 of earthlings. So if we count roshi who can go toe to toe with jiren and the androids as earthlings, then yamcha might leave the other two in the dust. He even has the feats to back it up as he survived the crossfire of two gods of destruction trying to blow eachother up and doing the better against moro's counselor than tien.
He's never portrayed as the strongest human. Without out of universe sources, I certainly wouldn't peg him as such. And we was only the strongest in the buu saga, so you could argue Tien holding cell down meant he was stronger for that one arc
The out of universe sources are still canon, and are not sharply contradicted by any in-universe material. Not sure why they wouldn't be valid?
Krillin was retired from fighting all together when the Boo saga rolled around, while Tien had been training the entire time... Yet Krillin was still stated to be the strongest among the earthlings. IOW, if Krillin was still above Tien then, he would have certainly been stronger when he was actually training during the Cell saga.
Tien using the Kikoho against Semi-Perfect Cell is a gargantuan feat -- and like I've said a bunch of times now: IF it connected, Krillin is f*cked(same as if Tien gets hit by Krillin's DD.)
But if we're talking strictly power-levels(with massively haxx special attacks like the Kikoho and DD removed from the equation), I think you'd be hard-pressed to prove that Tien was on par with Krillin by the Android/Cell saga.
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I am tired of being caught in the tangle of their lives."